The motors mentioned above must satisfy various requirements such as high rotation precision, high speed, low cost, and low noise. Motor spindle bearing is one of the constituent elements that determine required motor performance. Fluid bearings are considered to have excellent characteristics in many respects with regard to the required motor performance and some have found actual applications in recent years.
Fluid bearings of this type are generally classified into two categories. One is the dynamic bearing, which includes means for generating dynamic pressure of lubricating oil in a bearing clearance. The other is the cylindrical bearing (whose bearing surface forms a true circle) which has no such dynamic-pressure generating means.
For example, in a fluid bearing device incorporated in the spindle motor of a disc device, such as an HDD, there are provided a radial bearing portion rotatably supporting a shaft member in a radial direction in a non-contact manner and a thrust bearing portion rotatably supporting the shaft member in a thrust direction. As the radial bearing portion, there is used a dynamic bearing having grooves for dynamic pressure generation (dynamic pressure generating grooves) in the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member. As the thrust bearing portion, there is used, for example, a dynamic bearing in which dynamic pressure generating grooves are provided in the end surfaces of the flange portion of the shaft member or the surfaces opposed thereto (the end surfaces of the bearing sleeve, the end surfaces of a thrust member fixed to the housing, etc.) (see, for example, Patent Document 1). In some cases, there is used, as a thrust bearing portion, a bearing supporting one end surface of a shaft member by means of a thrust plate in a contact fashion (a so-called pivot bearing) (see, for example, Patent Document 2).
Usually, the bearing sleeve is fixed at a predetermined position of the inner periphery of a housing; further, to prevent lubricating oil filled into the inner space of the housing from leaking to the exterior, a seal member is often arranged at the opening of the housing.
Patent Document 1: JP 2000-291648 A
Patent Document 2: JP 11-191943 A
A fluid bearing device of the above-described construction is composed of components such as a housing, a bearing sleeve, a shaft member, a thrust member, and a seal member; efforts are being made to enhance the working precision and assembly precision of each component in order to ensure a high level of bearing performance required as information apparatuses are improved more and more in terms of performance. At the same time, with the recent trend toward lower-cost information apparatuses, there is an increasing demand for a reduction in cost for such a fluid bearing device.
An important factor in achieving a reduction in cost for such a fluid bearing device is an improvement in the efficiency of the assembly process. In many cases, the bonding between the housing and the bearing sleeve, between the housing and the thrust member, and between the housing and the seal member is effected by an adhesive; it should be noted, however, that it takes a relatively long time for the applied adhesive to be cured, which is one of the reasons for the rather poor efficiency of the assembly process. Further, there is a fear of gas emission from the adhesive and a deterioration of the adhesive with the passage of time.
The above problems might be solved by adopting press-fitting as the fixing means; however, the press-fitting force could lead to a deterioration in dimensional precision of the components, and the sliding of the components on each other at the time of press-fitting could generate abrasion dust (particles).